1. Field of the Invention
The invention relates to an embroidering machine and, more particularly, to an embroidering machine, provided with a main motor and a detachable embroidering unit having an embroidery frame, capable of controlling the operating speed of the main motor according to the movement of the embroidery frame.
2. Description of Related Art
There have been proposed various mechanically or electronically controlled embroidering machines, provided with an embroidering unit having an embroidery frame for holding a workpiece, for stitching embroideries by the cooperative effect of the vertical reciprocation of a needle bar and the horizontal movement of the embroidery frame.
An embroidering machine proposed in, for example, Japanese Utility Model Publication (Kokoku) No. Sho 57-24305 comprises a presser bar, a presser foot support plate attached to the lower end of the presser bar, a presser foot pivotally supported on the presser foot support plate, a presser lever extending obliquely upward from the presser foot and capable of engaging the horizontal shaft of a needle clamp, a magnet provided on the presser foot support plate so as to swing in synchronism with the vertical movement of the needle bar, a reed switch disposed near and above the magnet so that the output signal thereof remains HIGH (ON signal) during a period from a moment when the needle bar reaches its uppermost position to a moment when the presser foot presses a workpiece to allow the embroidery frame of an embroidering unit to be moved during the period in which the output signal of the reed switch is HIGH.
The embroidery frame of this embroidering machine is able to move while the output signal of the reed switch is HIGH, and the operating speed of the main motor is set by operating the speed volume of the embroidering machine independently of the feed of the workpiece. Because the period in which the output signal of the reed switch is HIGH is very short, the operating speed of the main motor must be held at a relatively low speed to ensure that the embroidery frame can be surely shifted during the period even if the feed of the workpiece is relatively large.